Health impacts of diesel emissions (PDF, 1.02MB)

Health impacts of diesel
emissions
13 June 2014
Christine Cowie
www.smh.com.au
Diesel exhaust particles
• DEP consist of a carbon
core surrounded by trace
metals, quinones, VOCs
• The solid particulate
fraction consists mainly of
very small particles
typically <1 μm in size
• Fine and ultrafine
particles (UFP)
• Elemental carbon or
organic carbon or soot
used as a surrogate for
diesel in epi studies
Concern with diesel exhaust particles
• Small size allows for
high deposition rate
into the airways
• High surface area
allows better
adsorption of other
chemicals
How important are diesel emissions to
health?
IARC, 2013
Major report deeming ambient air pollution as a cause of cancer (Group 1)
PM also separately classified as carcinogenic to humans (Group 1)
IARC, 2012
Reclassified diesel
exhaust as a carcinogen
What does this mean?
The WHO classifies the cancer-causing potential of various substances into
four groups, depending on the evidence available in both humans
(epidemiological and chamber studies) and animals (toxicological studies):
Group 1 is used when a substance causes cancer in humans
Group 2A is used when a substance ‘probably’ causes cancer in humans
Group 2B is used when a substance ‘possibly’ causes cancer in humans
Group 3 is used when a substance is not classifiable in terms of its cancercausing properties in humans because the evidence is inadequate
Group 4 is used when a substance is ‘probably not’ a cause of cancer in
humans
Why?
• Decision based on findings from epidemiological studies of workers
exposed to diesel fumes.
• Recent large cohort study (US National Cancer Institute and NIOSH),
published in March 2012, of occupational exposure to diesel exhaust in
12,315 US miners.
• Increased the risk of dying from lung cancer (1.26, 95% CI: 1.09 to 1.44).
• Case-control study, in this group (comparing 198 miners who had died
from lung cancer with 562 miners who were alive at the time the ‘case’
died), found risk of lung cancer in workers increased with the length of
exposure time – dose response.
• Studies were in heavily exposed workers to diesel fumes, however WHO
recommends action to reduce exposure to diesel exhaust fumes should
encompass both highly exposed workers and the general population.
Other views?
• National Toxicology Program (NTP) (US) (includes the National Institutes
of Health (NIH), the Centers for Disease Control and Prevention (CDC),
and the Food and Drug Administration (FDA). Classified exposure to
diesel exhaust particulates as “reasonably anticipated to be a human
carcinogen,” based on limited evidence from studies in humans and
supporting evidence from lab studies.
• The US Environmental Protection Agency (EPA) classifies diesel exhaust
as “likely to be carcinogenic to humans.”
• The National Institute for Occupational Safety and Health (NIOSH) has
determined that diesel exhaust is a “potential occupational carcinogen.”
Other health effects?
•
•
Acute exposures:
• can cause irritation to the eyes, nose throat and lungs, nausea
• cough, lung function changes and asthma exacerbations
• increase in inflammatory markers
• act as adjuvants to allergen to increase allergic response (chamber
studies)
Chronic exposures
• Cough, sputum production, lung function decrements
• increased lung cancer risk
•
USEPA has set a Reference Concentration for diesel exhaust (includes DPM)
of 5 ug/m3.
•
The US Health Effects Institute-Panel (2014) to report (in 18 mths time) on
whether there is sufficient data form the recent studies to conduct a
quantitative risk assessment for general exposures (that is lower dose levels)
How important is air pollution to health?
BOD 2010 Comparative
risk assessment of BOD
project (Lim et al, 2012,
The Lancet):
DALYs-includes mortality
and morbidity effects
Notable in that it is an
unavoidable exposure &
relevant to the whole
population
Knowledge gaps: concentration response
functions (CRFs) of particulate matter (PM) at
low and at very high (peak) levels
• Is there a threshold of effect to
PM2.5?
PM2.5 short-term effects
• Substantial evidence of
associations at very low levels of
PM2.5
• No observed threshold of effect
WHO AQG

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